چكيده به لاتين
In order to reduce CO2 emissions from the decomposition of calcium carbonate during the firing of cement clinker, various measures have been used, one of which is the addition of natural minerals and industrial tailings while grinding clinker and preparing mixed cements such as pozzolanic heads; A dual and multiple additive mixing system is also considered. The aim of this study was to add a dual system of metakaolin and blast furnace slag to Portland cement with a total mixture of 15% by weight and to investigate their effect on the physical and mechanical properties of Portland cement at intervals of 3, 7 and 28 days. To identify the chemical composition and minerals in the raw materials, X-ray diffraction and X-ray fluorescence tests were performed on them. In order to obtain takaolin, kaolin was exposed to 800 ° C for 2 hours. To ensure the release of hydroxyl groups during this heat treatment, kaolin and metakaolin were subjected to Fourier Transform Infrared Spectroscopy, Differential Thermal Analysis and Thermal Analysis. Examination and comparison of the results of kaolin and metakaolin showed that OH bonds start to break at 400 ° C and there is no hydroxyl group in metakaolin at 800 ° C; By making compounds containing cement and 15% by weight of slag, cement and 15% by weight of metakaolin and finally cement and 7.5% of slag and 7.5% of metakaolin, the effect of these alternatives on Portland cement hydration products was investigated. The results of X-ray diffraction test showed a decrease or stability of the portlandite phase over time. In differential thermal analysis, the adsorption peak related to the decomposition of Portlandite phase decreases over time, which indicates the consumption of this phase due to the pozzolanic activity of alternative materials. This occurs in heat weighing analysis as weight loss in the temperature range of 400 to 550 ° C; Thus, with higher pozzolanic activity and more consumption of Portlandite phase, weight loss is less in this range. Compressive strength test showed that the simultaneous use of slag and metakaolin in cement increases the strength of the piece by 13% compared to the control sample after 28 days and reaches 42 MPa.
